Variable cryosurgical probe planning system

ABSTRACT

A cryosurgical system including a computer system programmed with software configured to perform the following steps: a) capturing at least one first view of a region of interest in a human body; b) capturing at least one second view of the region of interest; c) outlining the region of interest and at least one area outside the region of interest with the assistance of an operator; d) constructing a 3-dimensional model of the region of interest and the at least one area outside the region of interest utilizing the at least one first view and the at least one second view of the region of interest; and e) utilizing the 3-dimensional model of the region of interest and the at least one area outside the region of interest to determine at least one cryosurgical probe placement location.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a continuation of U.S. application Ser. No. 15/669,943, entitled“Variable Cryosurgical Probe Planning System,” filed on Aug. 6, 2017,which is a continuation of U.S. application Ser. No. 13/731,639,entitled “Variable Cryosurgical Probe Planning System,” filed on Dec.31, 2012 and issued Aug. 8, 2017 as U.S. Pat. No. 9,724,150, which is acontinuation of U.S. application Ser. No. 13/481,557, entitled “VariableCryosurgical Probe Planning System,” filed on May 25, 2012, issued Oct.22, 2013 as U.S. Pat. No. 8,562,593, which is a continuation of U.S.application Ser. No. 11/618,492, entitled “Variable Cryosurgical ProbePlanning System,” filed on Dec. 29, 2006, issued May 29, 2012 as U.S.Pat. No. 8,187,260. The entire contents of each of the aboveapplications are incorporated herein by reference for all purposes intheir entirety.

BACKGROUND OF THE INVENTION 1. Field of the Invention

Embodiments of the present invention relate to computer guidedcryosurgery and more particularly to a system for assisting an operatorin placing and operating at least one cryosurgical probe in a region ofinterest in a human patient.

2. Description of the Related Art

Cryosurgery involving the use of cryosurgical probe assemblies typicallyinvolves the use of cryoprobes that are each attached to a handle thatare, in turn, connected to a high-pressure fluid line attached to afluid source. Cryosurgical ablation of the prostate has generallyrequired relatively small iceballs, i.e. 4 cm diameter by 6 cm length.For other applications, for example, renal applications, relativelylarger iceballs are desired. Many other potential applications ofcryosurgery may also require larger iceballs such as to ablate renaltumors, hepatic tumors, and pulmonary and thoracic tumors. Relativelylarge iceballs may also be required for palliative intervention.

The ultimate goal in a cryosurgical procedure is to freeze all tumortissue by lethal ice to kill the tumor and not to freeze any benigntissue surrounding the tumor tissue by lethal ice to avoidcomplications. Due to variations of tumor size and shape, it has alwaysbeen a great challenge for a cryosurgeon to precisely place multiplecryosurgical probes into desired locations of a tumor and control themso as to generate an optimum lethal iceball that is tailored to fit thetumor.

SUMMARY OF THE INVENTION

In a broad aspect, embodiments of the present invention relate to acryosurgical system for assisting an operator in placing and operatingat least one cryosurgical probe in a region of interest in a humanpatient. The cryosurgical system includes a computer system beingprogrammed with software configured to perform the following steps:

-   -   a) capturing at least one first view of a region of interest in        a human body;    -   b) capturing at least one second view of the region of interest;    -   c) outlining the region of interest and at least one area        outside the region of interest with the assistance of an        operator;    -   d) constructing a 3-dimensional model of the region of interest        and the at least one area outside the region of interest        utilizing the at least one first view and at least one second        view of the region of interest; and,    -   e) utilizing the 3-dimensional model of the region of interest        and the at least one area outside the region of interest to        determine at least one cryoprobe placement location.

Another embodiment of the present invention is directed to acryosurgical system for assisting an operator in placing and operatingat least one cryosurgical probe in a region of interest in a humanpatient, the system comprising:

-   -   the at least one cryosurgical probe; and    -   a computer system configured to perform the following steps:    -   a) capture a first view of the region of interest;    -   b) capture a second view of the region of interest;    -   c) outline the region of interest and an area outside the region        of interest utilizing the first view and the second view of the        region of interest;    -   d) construct a 3-dimensional model of the region of interest and        the area outside the region of interest utilizing the first view        and the second view of the region of interest; and    -   e) utilize the 3-dimensional model of the region of interest and        the area outside the region of interest to determine i) the        number of cryosurgical probes to be utilized; ii) cryosurgical        probe settings; and iii) cryosurgical probe placement locations.

A further embodiment of the present invention is directed to acryosurgical system for assisting an operator in placing and operatingat least one cryosurgical probe in a first area of a human patient, thesystem comprising:

-   -   a computer system programmed with software configured to perform        the following steps:    -   a) capturing a plurality of first views of the first area;    -   b) capturing a second view of the first area;    -   c) outlining the first area and at least one second area of the        human patient;    -   d) constructing a 3-dimensional model of the first area and the        second area utilizing the plurality of first views and the        second view of the first area;    -   e) utilizing the 3-dimensional model of the first area and the        second area to determine at least one cryosurgical probe        placement location; and    -   f) providing a graphical overlay on an ultrasound image for        directing cryosurgical probe placement.

The resultant ice thus produced by the cryosurgical probes is optimizedfor a specific patient.

Although the present inventive principles will be discussed in detailwith respect to their application to the prostate they may have manyadditional applications. Some additional particular applications includeablation of renal tumors, hepatic tumors, and pulmonary and thoracictumors. Relatively large iceballs may also be required for palliativeintervention. Such additional applications involve the selection ofregions of interest and subregions within these regions in order toprovide the modeling.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart illustrating, in a broad aspect, the stepsimplemented by the software of the computer system of the cryosurgicalsystem of the present invention.

FIG. 2 is a more detailed flow chart of a preferred embodiment of thesteps of the computer system.

FIG. 3 is a flow chart of the probe placement algorithm of FIG. 2 .

FIG. 4A is a schematic illustration of a transverse view of the prostatecapsule showing parameters utilized by the computer system of thepresent invention, this transverse view being taken at a middle sectionof the prostate.

FIG. 4B is a schematic illustration of another transverse view of theprostate, this view being taken at the apex of the prostate.

FIG. 4C is a schematic illustration of another transverse view of theprostate, this view being taken at the base of the prostate.

FIG. 5 is a schematic illustration of a sagittal view of the prostatetaken at the center of the prostate.

FIG. 6 is a schematic illustration of a top view of the prostate.

FIG. 7 is a block diagram of a preferred embodiment of the cryosurgicalsystem of the present invention.

FIG. 8 is an example screen display showing a captured image of theoutline of the middle gland of the prostate on the transverse view.

FIG. 9 is an example screen display showing the utilization of the depthguide of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings and the characters of reference markedthereon, FIG. 1 illustrates, in a broad aspect, the steps implemented bythe computer system of the present invention to optimize usage ofcryosurgical probes for a specific patient. These steps are designatedgenerally as 10. In a first step, the computer system captures aplurality of transverse views of the prostate, as noted by numeraldesignation 12. It then captures a sagittal view of the prostate(process block 14). The capsule of the prostate, the urethra and therectal wall of the patient are outlined with the assistance of theoperator, utilizing the captured plurality of transverse views and thecaptured sagittal view (process block 16). A 3-dimensional model of theprostate, the urethra and the rectal wall is constructed utilizing theoutlines noted above (process block 18). The 3-dimensional model is usedto determine i) the number of cryosurgical probes to be utilized; ii)probe settings; and, iii) probe placement positions (process block 20).The computer system used may be, for example, a PC running on theMicrosoft Windows operating system.

Referring now to FIG. 2 a more detailed flow chart is presented,designated generally as 22, illustrating the steps provided by thecomputer system. Preliminary steps include running a pretest to assuresystem integrity (process block 24). A cryosurgical probe is dipped intosterilized liquid and then cryogenic fluid is passed through thecryosurgical probe. If the cryosurgical probe functions properly, nobubble should appear in the liquid and an iceball should form at the tipof the cryosurgical probe. A received ultrasound image is adjusted(process block 26) utilizing an ultrasound software system, as will bediscussed in detail below. An option is then provided as to whethercryosurgical probe placement planning is to be provided using a singleultrasound image or multiple ultrasound images (process block 28).

If single image planning is selected (see decision block 30) thecomputer system confirms that single image planning has been selectedand then captures the middle gland on the transverse view (process block32). It then outlines the prostate, the urethra and the rectum wall onthe transverse, middle gland view (process block 34).

If multiple image planning is selected (see decision block 30) the stepsdiscussed with respect to FIG. 1 are applied. The computer systemcaptures a plurality of transverse views of the prostate, as noted bynumeral designation 12. It then captures a sagittal view of the prostate(process block 14). The capsule of the prostate, the urethra and therectal wall of the patient are outlined with the assistance of theoperator, utilizing the captured plurality of transverse views and thecaptured sagittal view (process block 16). A 3-dimensional model of theprostate, the urethra and the rectal wall is constructed utilizing theoutlines noted above. The 3-dimensional model is used to determine i)the number of cryosurgical probes to be utilized; ii) probe settings;and, iii) probe placement positions. (See process blocks 18, 20.)

Cryosurgical probe placement locations are then verified (process block36). A first criterion of verification is that each cryosurgical probeshould be positioned at least 5 mm away from a periphery of a urethra. Asecond criterion of verification is that a cryosurgical probe should bepositioned a safe margin away from a rectal wall. A third criterion ofverification is that a distance between two cryosurgical probes that arenext to each other should not exceed the sum of the radii of the lethaliceballs of the two cryosurgical probes. A fourth criterion ofverification is that a distance from a cryosurgical probe to a peripheryof a prostate should not exceed a radius of the lethal iceball of thecryosurgical probe. If all of these criteria are not simultaneously met,one or more of the least critical criteria may be compromised as desiredto provide functionality.

Graphical depth guide software is utilized to direct probe placementunder a depth guide (process block 38). This provides a graphicaloverlay on an ultrasound image of a sagittal view for assisting in theplacement of cryosurgical probes. As will be discussed in detail below,the graphical overlay includes a scale and an icon of a cryosurgicalprobe. The icon is divided into two parts. The first part is colored inblue representing a length of the lethal ice of the variablecryosurgical probe. The second part is colored in while representingnon-lethal ice of the variable cryosurgical probe. The distance from thegraphical overlay to the surface of the ultrasound probe changescorresponding to the variable surgical probe selected. The lengths ofthe lethal ice and non-lethal ice change in a manner corresponding to aselected setting of the variable cryosurgical probe. The icon can bedragged and dropped horizontally along the scale. After determining theoptimal location and the length of desired lethal ice by moving thedepth guide, an operator can select a setting on a variable surgicalprobe accordingly then insert it into a patient along the graphicaldepth guide. Cryosurgical treatment is then commenced (process block40).

Referring now to FIG. 3 the determination, by the computer system, ofvariable probe settings is illustrated, designated generally as 18, 20.This involves constructing the 3-dimensional model and utilizing the3-dimensional model to determine i) the number of cryosurgical probes tobe utilized; ii) probe settings; and, iii) probe placement positions.

In a first step, vertical distances from the urethra to top and bottomcapsules of the prostate are calculated for each captured transverseview (process block 42). Referring now to FIGS. 4A, 4B and 4C,transverse views of the prostate are shown along the largest (mid)section, the apex, and the base, respectively. At the apex, the verticaldistance from the top of the capsule to the urethra is denoted as UTR1.At the largest section, the vertical distance from the top of thecapsule to the urethra is denoted as UTR2. Similarly, at the base, thevertical distance from the top of the capsule to the urethra is denotedas UTR3. Although this example shows three sections captured, additionalsections can be similarly captured and vertical distances (UTRn)calculated. Similar calculations of vertical distances from the urethraat the bottom of the prostate capsule are also provided as denoted UTL1,UTL2, UTL3.

The prostate capsule is then scanned on the sagittal view, from left toright, and the vertical distances from the urethra to the top and bottomcapsule of the prostate at each vertical intersection on the sagittalview are calculated. As shown in FIG. 5 the sagittal view verticaldistances are denoted as USR1, USR2, USR3 . . . USRm defining a USRlist, and USL1, USL2, USL3 . . . USLm thus defining a USL list.

As can be seen in FIG. 3 , process block 46, the software then finds thepoints that closely match the distances on the sagittal view to thedistances on the transverse view. In other words, it finds a first ofcoordinates that closely match UTR1 from the USR list, UTL1 from the USLlist, UTR2 from the USR list, UTL2 from the USL list, . . . UTRn fromthe USR list, UTLn from the USL list.

Next, as noted in process block 48, the software calculates the centerheights of the prostate from the top to the bottom of the capsule of theprostate for each captured image on the transverse view, the transverseview center heights being denoted as HT1, HT2, HT3, . . . HTn. See alsoFIGS. 4A-4C.

As noted in process block 50, the prostate capsule is then scanned onthe sagittal view and the vertical heights calculated from the top tothe bottom of the capsule of the prostate, the sagittal view verticalheights being denoted as HS1, HS2, HS3, . . . HSm, defining an HS list.See also FIG. 5 .

A second set coordinates that closely match HT1 from the HS list, HT2from the HS list, . . . HTn from the HS list is then determined (processblock 52). The software then utilizes the first set of coordinates andthe second set of coordinates to calculate a final, optimized set ofcoordinates (process block 54).

The horizontal component, D2, of the distance between a first point ofthe optimized set of coordinates and a last point of the optimized setof coordinates, on the sagittal view, can then be calculated (processblock 56).

The horizontal components of the distances between each cryosurgicalprobe and the left of the prostate capsule are calculated for eachtransverse view, denoted as WR1, WR2, WR3, . . . WRn (process block 58).Similarly, the horizontal components of the distances between eachcryosurgical probe and the right of the prostate capsule are calculatedfor each transverse view, denoted as WL1, WL2, WL3, . . . Wln. See alsoFIG. 6 .

The software then utilizes selected WR1, WR2, WR3, . . . WRn; selectedWL1, WL2, WL3, . . . Wln; and, D2 to calculate the distances, D1, fromthe first point of the optimized set of coordinates 6 and the left ofthe prostate capsule, on the transverse view (process block 60).

Selected WR1, WR2, WR3, . . . WRn; selected WL1, WL2, WL3, . . . Wln;and, D2 are utilized to calculate the distances, D3, from the last pointof the optimized set of coordinates and the right of the prostatecapsule, on the transverse view (process block 62).

D1, D2 and D3 are then utilized to determine the length of a resultantlethal ice produced by the cryosurgical probes (process block 64).Appropriate settings of the cryosurgical probes based on the length ofthe resultant lethal ice can then be determined (process block 66).

Referring now to FIG. 7 , implementation of the computer system into acryosurgical system is illustrated, the cryosurgical system beingdesignated generally as 70. The cryosurgical system 70 includes acryosurgical probe system, designated generally as 72. The cryosurgicalprobe system 72 includes a plurality of cryosurgical probes 74; acontrol system 76 operatively connected to the plurality of cryosurgicalprobes 74; and, a cryogenic fluid source 78 operatively connectable tothe control system 76. It also includes temperature probes 80.

A temperature data acquisition system 82 acquires the temperature ofselected locations in the vicinity of the prostate utilizing thetemperature probes 80, cryosurgical probes 74 and the control system 76.

An imaging system, preferably an ultrasound system 84, and mostpreferably an integrated ultrasound system is utilized for obtainingselected images of selected locations in the vicinity of the prostate.

A computer system, designated generally as 86, is operatively connectedto the cryosurgical probe system 72 and the ultrasound system 84. Thecomputer system 86 implements the steps outlined above with respect toFIGS. 1-6 . It includes an integrated data processing system 88,suitable computer input/output devices such as a computer monitor,keyboard and mouse (collectively denoted as 90) and a video output 92.The video output 92 is provided so that an operator can convenientlyview the display at another location away from the computer monitoritself. A video input 94 is provided from an external ultrasound systemif an integrated ultrasound system is not utilized. The ultrasoundsystem software should be capable of adjusting contrast, brightness,gains, focus, depth, and imaging size of the ultrasound image.Furthermore, the ultrasound system software should be capable ofmeasuring a plurality of dimensions on an ultrasound image and ofchanging ultrasound views by toggling ultrasound transducers.

The fluid source may be, for example, a cryosurgical system such as thatmanufactured by present assignee, Endocare, Inc., Irvine, Calif. Such acryosurgical system typically utilizes argon gas from an argon gassource to provide Joule-Thomson cooling of the cryosurgical probes.Alternatively, nitrogen can be used. Alternatively, a fluid supplysystem can be utilized that does not require an external fluid supplysource. Heating of the cryosurgical probes is typically provided by ahelium gas source for providing a helium gas flow through the nozzle ofthe cryosurgical probe. This provides a heating effect. Such heating ofthe cryosurgical probes is provided to unstick the probes from thetreated tissue for cryoprobe removal. The cryosurgical probes may be ofthe type manufactured by present assignee, Endocare, Inc., Irvine,Calif.

A preferred cryosurgical probe is a variable cryosurgical probe such asthat disclosed and claimed in co-owned U.S. patent Ser. No. 11/613,054filed Dec. 19, 2006 to Duong, et al. entitled “Cryosurgical Probe WithVacuum Insulation Tube Assembly,” incorporated herein by reference inits entirety. Ser. No. 11/613,054 is assigned to present assignee,Endocare, Inc., Irvine, Calif.

Another variable cryosurgical probe is disclosed and claimed in co-ownedU.S. Pat. Publication US 20050192565 (U.S. patent Ser. No. 11/116,873),to Eum et al. entitled “Detachable Cryosurgical Probe with BreakawayHandle,” incorporated herein by reference in its entirety. Ser. No.11/116,873 is also assigned to present assignee, Endocare, Inc., Irvine,Calif.

Other cryosurgical probes are described in U.S. Pat. Publication No.20040267248 (U.S. Ser. No. 10/603,883) to Duong, et al., entitledDetachable Cryosurgical Probe, filed on Jun. 25, 2003, incorporatedherein by reference in its entirety; and, U.S. Pat. Publication US20050010200 (U.S. patent Ser. No. 10/828,031), to Damasco, et al.entitled “Detachable Cryosurgical Probe,” incorporated herein byreference in its entirety.

U.S. Pat. No. 6,643,535 issued to Damasco, et al. entitled “System forProviding Computer Guided Ablation of Tissue,” is also incorporatedherein by reference in its entirety.

A heat exchanger or cryostat is utilized to provide heat exchangebetween inlet gas and outlet gas. Although the heat exchanger ispreferably a coiled fin tube heat exchanger various other types of heatexchangers may be utilized such as a tube-in-tube sintered cryostat,threaded cryostat, coiled/sintered cryostat, or stacked coil cryostat.These different types of cryostats are disclosed and claimed in U.S.Pat. Publication No. 20050010200 (U.S. Ser. No. 10/828,031), entitledDetachable Cryosurgical Probe, filed on Apr. 20, 2004, discussed above.

FIG. 8 , is a screenshot of a computer display using present Assignee'sCryocare CS™ System, this screenshot being designated generally as 96.In this screen shot, the user has finished an outline 98 of the prostateand an outline 100 of the urethra, and he is performing an outline 102of the rectal wall. The user can drag each dot 103 around so that theoutline can fit the shape of the rectal wall. This corresponds toprocess block 16 of FIG. 1 .

Referring now to FIG. 9 , another screen shot is illustrated, designatedgenerally as 104 showing use of a depth guide. The computer system isprogrammed with graphical depth guide software, as discussed above,capable of providing a graphical overlay on an ultrasound image 106 forassisting in the placement of the cryosurgical probes. This depth guidedisplay format includes a first, (i.e. horizontal) scale 108 having aplurality of spaced markers. The cryosurgical probe icon 110 representsa cryosurgical probe. The cryosurgical probe icon 110 is positionedadjacent to the first scale 108. The cryosurgical probe icon defines akill zone 112 (typically colored blue) and a non-lethal zone 114 of thecryosurgical probe. The kill zone 112 represents a lethal temperaturerange and the non-lethal zone represents a temperature above the lethaltemperature range. The kill zone 112 and non-lethal zone 114 cooperatewith the spaced markers 108 to provide a visual guide for placing thecryosurgical probes. These zones are dependent on variable settings ofthe probe.

A second (i.e. vertical) scale 116 orthogonal to the first scale 108 hasa second plurality of spaced markers. The position of the cryosurgicalprobe icon 110 on the second scale 116 defines the distance of thecryosurgical probe 110 from an ultrasound probe, by referring to theimage 106.

Thus, in a broad aspect, the present invention is a cryosurgical systemfor assisting an operator in placing and operating cryosurgical probesin the prostate of a human patient, wherein the cryosurgical probes areinserted through the skin of the perinea! area of the patient and intothe prostate. The cryosurgical system includes a treatment system,comprising a computer system which is programmed with software capableof optimizing the resultant ice produced by the cryosurgical probes fora specific patient. An ultrasound imaging system is integrated with thetreatment system, wherein the computer software is programmed to adjustan ultrasound image.

Thus, while the preferred embodiments of the devices and methods havebeen described in reference to the environment in which they weredeveloped, they are merely illustrative of the principles of theinvention. For example, although ultrasound imaging has been described,certain applications may require guidance using various other imagingtechniques such as CT guidance or MRI.

Other embodiments and configurations may be devised without departingfrom the spirit of the invention and the scope of the appended claims.

The invention claimed is:
 1. A cryosurgical guide system for directingprobe placement during a cryosurgical procedure, the system comprising:a computer configured to perform the following steps: receive at leastone captured view of a region of interest in a patient; receiveindicators to identify the region of interest and an area outside theregion of interest based on the least one captured view; determinecryosurgical probe placement locations and cryosurgical probe settingsfor a plurality of cryosurgical probes to be used during thecryosurgical procedure; and verify the cryosurgical probe placementlocations and the cryosurgical probe settings based on the indicatorsthat identify the region of interest and the area outside the region ofinterest, and one or more criterion of verification, wherein theindicators are included in a graphical overlay on the at least onecaptured view, the graphical overlay including an outline of features ofinterest, a scale, and an icon representing placement of a cryosurgicalprobe with respect to the scale and the features of interest.
 2. Thecryosurgical guide system of claim 1, wherein the region of interest islocated within an organ selected from the group consisting of aprostate, kidney, liver, and lung.
 3. The cryosurgical guide system ofclaim 1, wherein the at least one captured view comprises a transverseview of the region of interest.
 4. The cryosurgical guide system ofclaim 1, wherein the at least one captured view comprises a sagittalview of the region of interest.
 5. The cryosurgical guide system ofclaim 1, wherein the at least one captured view is captured by anultrasound imaging system in communication with the system.
 6. Thecryosurgical guide system of claim 1, wherein the at least one capturedview is captured by a CT scan device or a MRI device.
 7. Thecryosurgical guide system of claim 1, wherein the computer is furtherconfigured to construct a 3-dimensional model of the region of interestand the area outside the region of interest on the at least one capturedview and the received indicators.
 8. The cryosurgical guide system ofclaim 1, wherein the indicators are received in response to an operatoroutlining one of a prostate, a urethra and a rectal wall on the at leastone captured image.
 9. The cryosurgical guide system of claim 1, whereina first criterion of verification includes that each cryosurgical probelocation is located at least a predetermined distance away from an organor other structure in the patient.
 10. The cryosurgical guide system ofclaim 1, wherein the cryosurgical probe icon defines a kill zone and anon-lethal zone.
 11. The cryosurgical guide system of claim 1, whereinthe scale includes a depth guide on an image of the region of interestand the area outside the region of interest.
 12. A method for assistingan operator in placing and operating cryosurgical probes in a patientcomprising: receiving at least one captured view of a region of interestin a patient; receiving indicators to identify the region of interestand an area outside the region of interest based on the at least onecaptured view; determining cryosurgical probe placement locations andcryosurgical probe settings for a plurality of cryosurgical probes to beused during the cryosurgical procedure; and verifying the cryosurgicalprobe placement locations and the cryosurgical probe settings based onthe indicators that identify the region of interest and the area outsidethe region of interest, and one or more criterion of verification,wherein the indicators are included in a graphical overlay on the atleast one captured view, the graphical overlay including an outline offeatures of interest, a scale, and an icon representing placement of acryosurgical probe with respect to the scale and the features ofinterest.
 13. The method of claim 12, wherein the region of interest islocated within an organ selected from the group consisting of aprostate, kidney, liver, and lung.
 14. The method of claim 12, whereinthe at least one captured view is captured by an ultrasound imagingsystem in communication with the system.
 15. The method of claim 12,wherein the at least one captured view is captured by a CT scan deviceor a MRI device.
 16. The method of claim 12, further comprisingconstructing a 3-dimensional model of the region of interest and thearea outside the region of interest on the at least one captured viewand the received indicators.
 17. The method of claim 12, wherein theindicators are received in response to an operator outlining one of aprostate, a urethra and a rectal wall on the at least one capturedimage.
 18. The method of claim 12, wherein a first criterion ofverification includes that each cryosurgical probe location is locatedat least a predetermined distance away from an organ or other structurein the patient.
 19. The method of claim 12, wherein the cryosurgicalprobe icon defines a kill zone and a non-lethal zone.
 20. The method ofclaim 12, wherein the scale includes a depth guide on an image of theregion of interest and the area outside the region of interest.